I'm not sure what you're asking. For any given variable, you can release its contents using undef. This is true regardless of the variable's scope (i.e., it's true for globals and lexicals both).

my $scalar = 'scalar of doom';
my @array = qw( things I want to forget );
my %hash = ( preservation_required => 'false' );

undef $scalar;
undef @array;
undef %hash;
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